In a case of bilateral diffuse superficial punctate keratitis with no mucopurulent discharge, what is the most likely origin if it stains with sodium fluorescein?

In the context of bilateral diffuse superficial punctate keratitis that stains with sodium fluorescein and presents without mucopurulent discharge, the most likely origin is viral. This condition is often associated with viral infections, particularly those caused by adenoviruses. The staining pattern seen with sodium fluorescein highlights areas of epithelial damage or cell loss, which is characteristic of viral keratitis.

Viral keratitis typically presents with subtle signs of irritation and inflammation, leading to punctate epithelial erosions. The absence of mucopurulent discharge is a significant clue, as bacterial keratitis would often involve more significant purulent discharge due to the inflammatory response.

In terms of dry eyes, while they can cause superficial punctate keratitis, the degree of bilateral involvement and staining would not typically be as pronounced in cases solely due to dryness. Similarly, a foreign body would likely present with specific signs of trauma and localized inflammation rather than the diffuse pattern observed in this case.

Thus, considering the clinical presentation and characteristic findings with fluorescein staining, viral etiology is the most plausible explanation.